(1) Field of the Invention
This invention relates to an olefinic elastomer composition. In particular, it relates to an olefinic elastomer composition which is excellent in mechanical characteristics, abrasion resistance, tackiness-free hand feeling, extrusion stability and quality stability.
(2) Description of the Related Art
For the purpose of improving the appearance and touch of automobile interior and exterior trim parts, domestic applicance parts, OA equipment goods, sporting goods, miscellaneous goods for daily use and the like and imparting thereto a design property, good feel to portions which are in direct contact with the hand, and a non-slip function or the like, there has heretofore very often been used a technique of using a flexible elastomer (rubber type) in exposed parts requiring a good appearance.
As this flexible elastomer, there have heretofore often been used flexible vinyl chloride resins and vulcanized rubbers in which an ethylene-propylene-diene rubber (referred to hereinafter as EPDM), a styrene-butadiene rubber or the like is used; however, for the economic reason of production costs and from the consideration for environmental problems and the like, substitution therefore of thermoplastic elastomers, representatives of which are styrenic thermoplastic elastomers, olefinic thermoplastic elastomers and the like, is now under extensive examination.
These thermoplastic elastomers are excellent in moldability for injection molding, extrusion molding, blow molding or the like and, in addition, excellent in flexibility and touch, and therefore, have been used in various fields.
In particular, in the case of the olefinic thermoplastic elastomers, those produced by subjecting a vulcanizable (cross-linkable), olefinic elastomer and polypropylene (referred to hereinafter as PP) to vulcanization reaction (cross-linking reaction) in the presence of a vulcanizing agent (cross-linking agent) while melt-mixing them in an extruder, namely the so-called dynamic vulcanization, have been extensively examined as substitutes for conventional materials used in automobile interior trim parts and the like, and have actually been adopted in many parts.
However, on the one hand, the conventional olefinic thermoplastic elastomers have a problem of tackiness upon contact with hands or damageability and a problem that the abrasion wear is large, and the like in parts which are directly contacted with the hand such as grip and the like and external parts which always contact with other portions such as pedals and the like. The replacement of the above-mentioned flexible vinyl chloride resins with a substitute which is relatively excellent in these touch characteristics and scratch resistance and characteristics such as abrasion resistance and the like has been delayed under the existing circumstances.
On the other hand, for these problems, there have been proposed a thermoplastic elastomer composition composed of a dynamically vulcanized, olefinic thermoplastic elastomer and a polydimethylsiloxane having a dynamic viscosity of at least 100,000 centistokes (JP-A-11(1999)-35,750) and a thermoplastic elastomer composition composed of a styrenic thermoplastic elastomer, a dynamically vulcanized olefinic thermoplastic elastomer, a paraffin oil and a polydimethylsiloxane having a dynamic viscosity of at least 50,000 centistokes (JP-A-8(1996)-319,383), and the publications state that the tackiness and damageability are improved. In addition, a thermoplastic elastomer composition composed of a dynamically vulcanized, olefinic, thermoplastic elastomer having added thereto a polydimethylsiloxane having a dynamic viscosity of 50 to 5,000 centistokes (JP-A-5(1993)-1,183) is proposed and the publication states that the mold release characteristics are improved. However, it is silent on abrasion resistance, and requires a further improvement.
In view of such a situation, this invention aims at providing an olefinic elastomer composition having no problems as mentioned above.
The present inventors have diligently examined improvement of, particularly, the abrasion resistance of an olefinic elastomer composition, and as a result, have surprisingly found that by blending a specific polyorganosiloxane with a specific ethylene-xcex1-olefin copolymer, the abrasion resistance is enhanced remarkably, and accomplished this invention. That is to say, this invention has been completed by finding that with an ethylene-xcex1-olefin copolymer prepared using a non-metallocene catalyst, the abrasion resistance is improved only when a ultra-high-molecular-weight polyorganosiloxane is used; however, with the above copolymer obtained using a metallocene catalyst, excellent abrasion resistance is developed even when a polyorganosiloxane in a relatively low viscosity region is used.
That is, this invention is a partially or completely vulcanized, olefinic elastomer composition comprising (A) 1 to 99 parts by weight of an ethylene-xcex1-olefin copolymer prepared using a metallocene catalyst which copolymer consists of ethylene and an xcex1-olefin having 3 to 20 carbon atoms and (B) 1 to 99 parts by weight of a polypropylene resin, provided that the total amount of the components (A) and (B) is 100 parts by weight, wherein (C) a polyorganosiloxane having a dynamic viscosity at 25xc2x0 C. of at least 5,000 centistokes is contained in a proportion of 0.01 to 20 parts by weight per 100 parts by weight of a total of the components (A) and (B), particularly the above vulcanized, olefinic elastomer composition in which the dynamic viscosity of the component (C) is at least 5,000 centistokes but less than 100,000 centistokes.
The vulcanized (cross-linked), olefinic elastomer composition of this invention has remarkably improved abrasion resistance and is excellent in hand feeling and scratch resistance. Moreover, as a result of the enhancement of the dispersibility of the polyorganosiloxane (C), the above composition is excellent in extrusion stability and quality stability. In addition, the vulcanized, olefinic, thermoplastic composition of this invention can be widely used in interior automotive trim materials, representatives of which are instrument panel cover, air bag cover, handle, shift knob lever, window molding, pedal pad and the like, and further in uses including domestic appliances, miscellaneous goods, daily necessaries, sporting goods, constructional materials, sheets, films and the like, and the commercial values thereof are very high.